Paper



Aug. 3, '1 937.

L C. GATES PAPER Filed Oct. 9, 1935 R g I 7 79 5 X /oaao v Pam,

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Patented Aug. 3, 1937 UNITED STATES PATENT OFFICE PAPER ApplicationOctober 9, 1935, Serial No. 44,266

r 10 Claims.

This invention relates to an improved uncoated paper for printing andvarnishing, and it comprises a bright, well formed," opaque paper stockhaving an extremely smooth, highly finished, dense,-closed up surfaceuniformly impenetrable to varnish. The paper embodies anovel combinationof superior printing and varnishing properties which renders itparticularly valuable for brilliant .and attractive can, bottle andpackage labels, posters, liners, covers and the like. I There is a largedemand for paper of a type suitable for receiving a. coating or printingof varnish. In some cases certain uncoated printing papers have beenused for this purpose, but the excessive penetration of the varnish intothe sheet has restricted the usefulness of 'uncoated papers to inferiorgrades of work. For the better jobs it has been necessary to resort tospecial kinds of coated paper, employing a varnish,re-- sistant coating.varnishing quality coated label paper is not only more costly thanuncoated label paper, but also costlier even than regular coated labelpaper. The present invention offers an entirely satisfactory,inexpensive, uncoated substitute for the varnish quality coated paper.Moreover, my paper is superior to coated paper in that it is free fromany tendency to crack along the fold when the paper is sharply .creased.

A paper to have good varnishing qualities must have a smooth, impervioussurface, so that penetration by the varnish is minimized, and it mustretain the varnish film uniformly on the surface. This means that thevarnish, whether spirit varnish applied by a roll, brush or scraper, oroil 5 varnish applied by a printing operation (overprint varnish) shouldgive a high glossy finish without mottle; it should not enter anddiscolor the paper appreciably, and it should notproduce an appreciableincrease in the transparency of 4c the paper. As stated above, thesequalities are usually associated only with certain grades of speciallycoated paper, but my paper, although uncoated, has varnishing qualitiessubstantially equal to those of the better grades of varnish qualitycoated papers.

My product has a number of the properties .of glassine, but isfundamentally different from glassine in that it is opaque. Glassineis-smooth and highly impervious, and possesses excellent .50 varnishingqualities, but its transparency renders it entirely unsuitable for thepurposes to which varnishing grades of paper are put. Generallyspeaking, my new paper maybe said to have the surface characteristics ofglassine, and

the body stock characteristics of good printing paper. Thus, likeglassine, the paper has'a slick, dense, impervious, uniform, extremelysmooth surface,' which resists penetration by varnish. On the otherhand, the body of the paper has the brightness, opacity and uniformformation of a supercalendered book paper. As for printing qualities,its smooth surface permits the faithful reproduction of fine half tonesand deep, uniform solid blacks. Ink absorption, although slight, isuniform. The ink in this case dries largely by oxidation and gives abrilliant, glossy effect of exceptional merit. It should be noted thata. paper having good printing and varnishing properties'embodies anunusual combination. The paper of the present invention, which combinesthese qualities, and which is nevertheless free of any special loading,coating or impregnating materials, is new in the art.

In manufacturing this paper I may use the librous materials ordinarilyused in a book or label paper. The beating, jordaning and paper machineoperations should be carrled out to produce a paper having the uniform,closed up formation of a book paper, rather than the wild formationcharacteristic of a bond or kraft paper. At the same time it should nothave the dead beaten properties of a glassine. Undisintegrated fiberclumps alternating with comparatively open areas are to be avoided. Theyprevent uniform ink and varnish reception. It is desirable thatthe-stock have a high densometer value, for ex ample, 300 seconds 'ormore, as determined on the Gurley densometer instrument. If desired, itmay carry a surface filling or surface sizing.

The paper is then supercalende'red. A supercalender employingalternating smooth metal and yielding-rolls is suitable for thisoperation. The

. side of the paper first contacting with the metal supercalender rollsis well moistened just prior to its contact with the metal roll. Thismay be done by the direct application -of liquid water by means of arolldipping into a bath whereby an excess is applied to the paper and thepaper then passes over a small rod and the excess is removed. Or a heavysteam shower may be applied to the paper or to the metal calender roll.

The applied moisture is not permitted to distribute itself through thesheet, but is confined as much as possible to the surface. Thecombination of heavy pressure in the supercalender and the moist surfaceon the aforedescribed stock produces a paper having the desired smooth,dense, impenetrable surface, without adverselyv affecting the bodycharacteristics of the paper. The surface layers resemble glasslne. Thisprocedure, it should be noted, is directly the opposite of the normalsupercalendering practice of uniformly compacting the paper. If only oneside of the paper is to be given a high finish of the 5 kind described,it may be givenonly a single pass through a calender stack in which onlyone side is contacted with the metal rolls, and then as it leaves thecalender stack, the other side may be steamed or otherwise moistenedsufiiciently to remove the curl produced by the one side calendering asdescribed in my application Serial No. 749,109. If, however, both sidesof the paper are to be finished, the steaming to remove the curl isomitted and the paper is returned for another passage through thecalender stack in which the other side of the paper is moistened andcontacted with the metal rolls of the calender stack as described.

Certain processes of water finishing and calender staining have beenapplied to various wrapping papers, bag papers, etc., where strength andfinish are important factors. But papers produced in these ways are wellrecognized as being entirely unsuitable as varnishing papers on acsuchpapers is mottled and spotty in contrast to the uniform high gloss of myproduct. My paper is further characterized by having a high even finish.The finish has the uniformity of a good supercalendered book paper, butis considerably higher. When tested on the Bausch 8: Lomb glossmeter thefinish in general is in excess of 40. Supercalendered book paperscommonly give readings of 22 to 32, and water finished bag paper and M.G. papers usually give readings between 2'7 and 42.

My invention includes paper of all basis weights. As stated above, oneof the requirements for my new paper is that the fibers be evenly mattedto-' 40 gather to give a well formed, closed up, uniform formation tothe paper, such as corresponds to a good grade of book papers.Quantitative measurements and standards for formation have beenestablished in the industry. Numerical measure- 5 ment. of formationdepends to some extent on basis weight. Thus a double thickness of asheet having a given formation would appear to have a better formationthan it really has. The formation value required for my paper may bedefined as that of a sheet of 60 pounds basis weight (25 x 38 inches-500sheets), with a formation of at least 66 as defined by the CentralGrading Committee (executive authority) of the Book Paper ManufacturersAssociation (1934). In 55. other words, a heavy sheet, for example,would have to have the formation equal to a 60 pound sheet having aformation value of at least 66; the determination of which is a simplematter for those skilled in the art, by an examination 60 of the surfacestructure. Formation should be equal to or better than that required ina B grade machine finished book paper, as defined by the aforesaidcommittee.

The paper embraced by my invention is read- 6 ily distinguished fromglassine by its much greater brightness and opacity. Itis characterizedby having a brightnessof at least 66 as defined by the Central GradingCommittee (executive authority) of the Book Paper Manufacturers As- 70sociation (1934). The opacity of my paper approximates that of asupercalendered book paper. If both sides of the paper are provided withthe varnishing quality surface, the opacity will be somewhat lower.

1 In the accompanying drawing I have shown count of uneven absorption. Avarnish job on graphically the opacities of several samples of my paperof different basis weights, opacity determination being made on theBausch 81 Lomb opacimeter and basis weights being expressed as poundsfor 500 sheets 25 x 38 inches. The area between the curves AA and DD'embraces the opacities of white supercalendered book papers asordinarily manufactured. The curve GG is typical of glassine. It will beseen that the opacities of samples of varnishing surface one side paperlie within or very close to the supercalendered zone, while the samplesof varnishing surface two sides paper are a trifle less opaque. In anycase, the opacity of my paper for any given weight will exceed thatshown by the curve BB. It will be noted that this is far in excess ofopacities for glassine. Colored or tinted paper made according to thepresent invention is a very attractive product.

My paper, although uncoated, has varnishing qualities substantiallyequal to those of coated papers generally recognized'in the art as beingof varnish quality. On brushing a definite quantity of standard spiritvarnish on the new paper and on varnish quality coated papers, by way ofcomparison, it is seen that the new paper shows gloss, lack ofdiscoloration and lack of transparency equal or superior to the averagesample of varnish quality coated papers.

Although there is no generally accepted quantitative test for thevarnishing quality of paper, it has been observed that the time requiredfor castor oil to completely saturate a sheet of uncoated paper bears adefinite relation to the absorption of printing ink and certain kinds ofvarnish. A method of performing this test is to lay a piece of the paperto be tested on the surface of the oil and note the time in secondsrequired for complete saturation. The paper should be conditioned andthe test conducted at 70 F. and 50% relative humidity. U. S. P. castoroil should be used and should have a viscosity of about 9 poises at thetime of the test. p

The time for saturation of machine finished and supercalendered bookpapers, other things being equal, is roughly proportional to the squareof the basis weight. The average saturation time for book papers isapproximately one eighteenth of the square of the basis weight (25 x 38inches- 500 sheets) and will rarely if ever exceed this value by morethan 150 seconds. The papers of my invention, on the other hand, willalways exceed the value stated by more than 200 seconds and will ingeneral exceed it by 300 seconds or more.

One paper within the scope of the invention is exemplified by thefollowing: The stock consists of about equal proportions of sulflte andsoda pulp, with asmall amount of mineral filler and moderately sizedwith rosin size, and both sides having a varnishing surface. Basisweight (25 is as inches-500 sheets) Varnish-Equal to varnish qualitycoated paper This application is a continuation-in-part of myapplication Serial No. 749.109, filed October 19, 1934.

at least equal to that of a paper of basis weight 60 pounds (25 x 38inches-500 sheets) having a formation of 66 as defined by the CentralGrading Committee of the Book Paper Manufacturers" Association (1934),an opacity on the Bausch &

Lomb opacimeter greater than about 71 for basis weight 35, 76 for basisweight 40, 79 for basis weight 45, 81 for basis weight 50, 83 forbasisweight 55, 85 for basis weight 60, 86 for basis weight 65, 87 for basisweight 70, 88 for basis weight 75, 89 for basis weight 80, 90 for basisweight 90, 91 for basis weight 105, and 92 for basis weight 115, asshown on curve BB of Fig,- ure 1, and varnishing. propertiessubstantially equivalent to' those of a varnish quality coated paper.

2. An uncoated printing paper produced by the process defined in claim 8and having a varnish quality substantially equal to that of a commercialvarnish quality coated paper, said paper being characterized by having asmooth, dense,

uniformly impervious surface of the nature ofglassin; and an opacitywhen measured on the Bausch & Lomb opacimeter greater than about 71 forbasis weight 35, 76 for basis weight 40, 79

for basis weight 45, 81 for basis weight 50, 83 for basis weight 55, 85for basis weight 60, 86 for basis weight 65, 87 for basis weight .70, 88for basis weight 75, 89 for basis weight 80, 90 for basis weight 90, 91for basis weight 105, and 92 for basis weight 115, as shown on the curveBB of Figure 1.

3. An uncoated printing paper produced by the process defined in claim 8and having a var- 'nish quality substantially. equal to that ofcommercial varnish quality coated paper, said paper being'characterizedbyhaving a smooth, dense, uniformly impervious surface of the nature ofgiassine, a finish of at least 40 on a standard Bausch 8r Lombglossmeter and an opacity, when measured on the'Bausch & Lomb opacimetergreater than about 71 for basis weight 35, 76 for basis weight 40, 79for basis weight- 45, 81 for basis weight 50, 83 for basis weight 55,.85 for basis weight 60, 86 for basis weight 65, 87 for basis weight 70,88 for basis weight 75, 89 for I basis weight 80, 90 for basis weight90, 91 for basis weight 105, and 92 101- basis weight 115, as shown oncurve BB of Figure 1. i

4. A varnishing quality, uncoated, printing paper produced by theprocess defined in claim 8 and characterized by having a smooth, dense,

uniformly impervious surface of the nature of giassine, a formation atleast equal to that of a paper of basis weight 60 pounds (25 x 38inches- 500 sheets) having a formation of 66 as defined by the CentralGrading Committee of the Book basis weight 80, 90 for basis weight 90,

.Paper Manufacturers Association (1934), an'

opacity on the Bausch 8r Lomb opacimeter greater than about 71 for basisweight 35, 76 forbasis weight 40, 79 forbasis weight 45, 81 for basisweight 50, 83 for weight 55, basis weight'60, 86 for basis weight 65,basis weight 70, 88 for basis weight 75, 89 for 91 for basis weight 105,and 92 for basis weight -115, as

85 for i 87 for 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 90, 105 and 115,respectively, and when conditioned and tested at- 70 F. and 50% relativehumidity, a saturation the flotation test on U. S. P. castor oil havinga viscosity at the time of. the test of about 9 poises.

6. An uncoated printing paper produced by the process defined in claim 8and characterized by having a smooth, dense, uniformly impervioussurface of the nature of giassine, an opacity on the Bausch 8r Lombopacimeter greater than 71, 76, 79, 81, 83, 85, 86, 87, 88, 89, 90, 91and 92 for basis weights 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 90, 105and 115, respectively, a finish of at least 40 measured on a standardBausch- 8a Lomb glossmeter, and when conditioned and tested at 70 F. and50% relative humidity, a saturation eighteenth of the square of thebasis weight, in the flotation test on U. S. P. castor oil having aviscosity, at the time of the test, of about 9 poises.

7-. Paper as defined in claim 5 further characterized by a finish of atleast 40 on a standard Bausch 8: Lomb glossmeter. I

8. Process of making a varnishing grade of uncoated paper whichcomprises, temporarily softening at least one surface of an evenlyformed paper web by adding sufiicient moisture thereto to produce whensu'percalendered a surface of the nature of giassine, andsupercalendering the web before the moisture has had time to penetrate9. Process as defined in claim 8 in which only one surface of the paperis moistened and supercalendered and the other surface is moistened,subsequent to the supercalendering operation, to a degree sufficient tosubstantially eliminate the curl caused by the supercalendering.

10. An uncoated printing paper produced by the process defined in claim8, one surface of said paper having a varnish quality substan- .tiallyequal to that of a commercial vamlsh quality coated paper and beingcharacterized by having a smooth, dense, uniformly impervious surface ofthe nature ofgiassine and the-other surface beingsubs'tantially free, ofsupercalenden finish, saidpaper being substantially free of curl andhaving an opacity when measured on the Bausch 8; Lomb opac'lmetergreater than about 71 for basis weight 35, '76 for basis weight 40, 79for basis weight 45, 81 for basis weight 50, 83 for basis weight 55, 85for basis weight 60, 86 fol" time in seconds of not less than 200 plusoneeighteenth of thesquare of the basis weight in basis weight 65, 87.for basis weight 70, 88 for basis weight 75, 89 for basis weight 80, 90for basis weight 90, 91 for basis weight 105, and. 92

for basis weight 115, as shown on the curve BB of Figure 1.

LEROY C. GATES.

